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I'm trying to fabricate some caliper brackets for a set of radial mount calipers for a Honda Prelude & ITR. The problem is that there isn't enough material for both the OEM bolts that attach the caliper bracket to the knuckle and for the radial mount studs for the caliper. So now I'm thinking of making some brackets out of mild steel that I'll weld to the knuckle. Instead of the 12mm bolt hole for the OEM caliper bracket bolt, I was thinking of machining two bosses on the caliper bracket to locate the bracket on the knuckle. Then TIG weld the bracket to the knuckle everywhere it contacts the bracket and on the bosses that will be located in the OEM caliper bracket holes.

So my questions are, what would be the best steel to machine the bracket from, what kind of filler would be best, and would the knuckle require any heat treating afterwards? If the knuckle requires heat treating, will that warp the wheel bearing bore any?

Niles

I've got a fourth gen, and the knuckles appear to be forged. You don't want to weld to them. More than likely they are a mild to mid carbon steel and you could weld to them, but by heating and cooling them the grain structure of the metal changes and you loose some of the strength that the factory gave you by forging them.
Are you thinking of putting these brakets in the back or the front? The caliper brakets on the rear hubs on my prelude come apart from the knuckle by removing the four bolts through the knuckle. The best option in that case is to replace that whole braket instead of trying to weld to the knuckle or the existing braket. This solution would be stronger and lighter.
In the front the mounting ears for the calipers are in integral to the knuckle. In that case if you really needed something different I would say fabricate a simple braket that bolts to the exisitng ears on the kuckle, and to the calipers you are trying to fit. That would be the safest, most reliable solution.

117

How did you determine that the knuckles are forged and not cast? If it's forged, I may be out of luck.

I don't believe that brackets that bolt to the knuckle with the radial mount studs are going to work. There isn't enough room, as the spacing on the radial mount studs is 152mm, IIRC. There's only enough room to get 12mm depth on the 12mm radial mount stud because the threaded hole for the OEM caliper bolts is right under the hole for the radial mount studs. That's not enough thread engagement IMO.

That's why I was thinking of welded a bracket onto the knuckle. If I could weld the bracket on, I'd eliminate the OEM caliper bolts, which means the threaded hole for the radial mount stud could be as deep as it needs to be (18mm to 20mm).

This is for the front, BTW. No real reason to upgrade the rear calipers.

The reason why there isn't much room is that we're trying to get these to fit under 15" wheels. If we were using 16" wheels, we'd have no problem.

Niles

Are you using the newer wilwood radials? I've seen radial calipers getting big with the sport bike crowd, I was wondering when people would start fitting them to cars. Any restrictions in the rules? I might not understand exactly what you mean, but I think I do. Without knowing 100% what your limitations are I would say the other solution I've seen is to make a bracket (basically a plate with some holes/bosses) that fits behind the stock mounting points, and has the bolt holes for the caliper bracket (with the studs) 'rotated' around from the stock holes in order to give you the clearance you need. You could move your caliper towards or away from the center of the wheel this way. There's plenty of space on the back of the knuckles for as thick of a bracket and as long of a bolt as you'll need. You would need to fabricate new dust shields, or cut up your current ones, as something like this would take up some space.

117

I can't move the caliper much further inboard than it is now. I run into clearance problems with the back side of the rotor hitting the caliper mounting bolts (the bracket is already mounted on the opposite side as the OEM caliper bracket in an attempt to gain as much clearance and stiffness as possible), and with much more offset, the rotor face would be very, very close to the lower ball joint boot. In other words, I can't move the caliper any further inward than it is already.

I have Wilwood 6 piston calipers on the car now. The Wilwood's do not have this problem because the posts on the radial bracket are quite tall. The caliper we're trying to fit is an Alcon, whose mounting posts are 0.8" shorter, and hence causing the issue we're running into.

I've already modeled the bracket in SW in various configurations. The bolt on bracket might work, but the amount of material in the critical areas is questionable.

The rules allow any rotor/caliper combination, so I wouldn't expect the welded bracket to be an issue. I'm not worried about the rules as much as I am the structural integrity of the knuckle post-welding.

So how did you determine that the stock knuckles are forged?

Rocket Man

I'm pretty sure the knuckles are cast steel. I used a hammer and a chisel and the metal rolls over on its self and doesnt chip. I have also welded on the knuckles before and it flows and welds similar to cast steel.

BrakeExpert

Heh, I had to laugh when I read this. I know our cars are great, but we aren't lucky enough to get forged knuckles. In fact I think the only forged part we got is the crank. But anyway, the knuckles are cast steel, though a very well engineered piece.
I hate to threadjack, but I have personally built a bracket for radial calipers out of a simple bar of cold rolled carbon steel and tapped 4 holes. I bolted the RL calipers over 12.6" rotors on most Honda knuckles and over 11.8" rotors on DX civic knuckles. The Civic knuckle DX setup requires grinding the head off the bolt a little.

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Here's the problem:



I can only get around 12mm of depth on the threaded hole for the radial mount studs. So that's 10mm to 11mm worth of thread engagement. Not enough for a brake application, IMO.

The hole that is perpendicular to the drawing surface is the hole for the bolt to mount the caliper to the knuckle. The other hole is obviously the radial mount stud bolt hole. Both are for 12mm bolts.

Niles

Cant' you rotate the mount holes for the radial pins so they are just far enough away from the the holes for the mounts that you can get away with either being as thick as you want? Alot of brake kits do that kind of thing.

I'm going to be back in the garage tonight I'll take another look at the knuckles. Based on thier design and the flash at the parting of the mold I was assuming they were at least low pressure forgings. Casting a part like this without some serious secondary processing would be a bitch because of the height of it. Of course the height does rectify errors in warping and manufacturing but anyways I'll go take another look latery.

Niles

So I was back in the garage playing with the car and I'm going to go ahead and say I was right. Look at the parting line. That tells you it came out of a two sided forging die. Look at the webbing. If this part was cast it would be prohibitivlely expensive to try to maintain the radii and thicknesses as well as the imprinted identification symbols. It's easy to get that kind of webbing on aluminum castings in steel dies, but they wouldn't cast the steel uprights in steel dies because they would just burn though dies, and steel castings crack when there's significant differences in thickness right next to each other. IF they were final cast and not just rough cast to this shape they would have had to be investment cast (possibly sand cast) and then machined. That wouldn't leave the parting line or reliefs. Even with investment casting they would have a difficult time getting the ID symbols and such to come out cleanly. Sand casting they would have stamped them in instead of casting them so they stuck up from the surface.
So they were cast to rough shape, then forged. Open your textbooks or ask your fiendly neighborhood machinist, they'll tell you the same thing.

Rocketman: chiseling and weld behavior has alot more to do with the actual material and not the post processing. Forging will increase strength and resistance to cracking under cyclic fatigue, but it doesn't really affect machinabiliaty. You should also probably go into the hybrid forum and tell eveyone what happened to your car so they stop bumping your thread once a week asking about it.

Just so you guys don't think I'm coming out of nowhere, I'm a mechanical engineer with a background in manufacturing, so if you don't believe me I don't really care, but if you don't believe honda's own press releases, like this one:
http://corporate.honda.com/pre...01322
then, well, back to the drawing board...
The article mentions the lower control arms being forged, If you look at the arms, and look at the uprights, you'll see all the same features. Features of a forged part. The part line, the webbing with clean and precise radii, and similar ID symbols.

so, to the OP you can weld to it, and I'm sure it will be fine, but you'll give up fatigue resistance, even with a heat treat because of changes to the crystal matrix of the metal. I wouldn't do that on a race car. Instead I would just offset the holes for the mounts from the holes for the studs so you can make the thread engagement as deep as you want.

peace
Niles

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I'm going to see if I can do the offset hole trick without putting the caliper at a weird angle, which would cause problems with caliper bleeding.

tony1

FWIW, i did some welding on an OEM honda upright that i converted to a Mac strut setup on a drag car. Everything machined and welded good. I put a couple "just in case" bolts in it to make me sleep better though. lol

Niles

Tony1>all.

All I can ever say is; nice work!

m R g S r

what is the point or advantage of radially mounted calipers? i know almost every new sport bike has em. . . .but not many cars run them. . . ?

EGPrelude

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by m R g S r &raquo;</TD></TR><TR><TD CLASS="quote">what is the point or advantage of radially mounted calipers? i know almost every new sport bike has em. . . .but not many cars run them. . . ?</TD></TR></TABLE>

you get more choices in multi-piston mono-block calipers. most big brake kits with monoblock calipers are radially mounted.

m R g S r

so thats it? not heat dissipation advantages, better braking, stronger caliper etc?

Because like i said, every new sport bike has radially mounted calipers like its the hottest new ishhhh

JDMCRX

iTrader: (2)

Bump curious too